W. G. Weber et al. / Tetrahedron Letters 47 (2006) 4771–4774
Table 1. Synthesis of compounds 1a–i
4773
the temperature below 40 ꢁC. Stirring was continued until
% Yielda
the magnesium had been consumed. The flask containing
the Grignard solution was then placed into a cooling
bath (ice/water), and carbon disulfide (7.6 g, 100 mmol)
was added dropwise. The internal temperature rose and
the solution turned red. Stirring was continued at room
temperature for 1 h and the reaction then cooled down
again to 0 ꢁC. A solution of p-tosyl chloride (9.5 g,
50 mmol) in 40 ml of dry THF was added dropwise over
30 min. The colour changed from red to purple. The
solution was stirred for another hour at room tempera-
ture and then the solvent was removed under reduced
pressure and the residue kept overnight in a freezer.
The solidified material was washed repeatedly with
water and recrystallized from acetone or acetonitrile.
Purplish-red crystals, mp 92–93 ꢁC (acetone), 8.4 g
(55%). The mother liquor contained further product
(4.5 g), which could be purified by column chromatogra-
phy. 1H NMR (300 MHz, CDCl3) d (ppm): 8.10 (d,
J = 8.2 Hz, 4H, H-2/6), 7.62 (t, 2H, H-4), 7.46 (t, 4H,
H-3/5); 13C NMR (75 MHz, CDCl3) d (ppm): 220.13
(C@S), 143.98 (C-1), 133.32 (C-4), 128.85 (C-2), 127.76
(C-3).
R–CS–S–S–CS–R
R
Method
1a
1b
1c
1d
1e
1f
C6H5CH2S
A1/A2
A1
A1
A2
B1
B1
B1
B2
A2
70/80
81
61
77
55
73
59
61
77
C12H25
S
n-C4H9S
H5C2O
C6H5
4-(H3CO)C6H4
4-FC6H4
C4H3S
1g
1h
1i
(CH3)2N
All products provided satisfactory spectroscopic data.
a Yield for recrystallized products.
200 mmol) in 80 ml of THF at 30 ꢁC, was stirred for
30 min after dropwise addition of the bromide and then
decanted into a new flask. The residual metal was
washed with 20 ml of THF and the solvent combined
with the Grignard solution. After cooling to room tem-
perature, 145 mg (1 mmol) of copper(I) bromide and
carbon disulfide (10.65 g, 140 mmol) were added. The
temperature rose to 40 ꢁC and the solution turned red.
The reaction mixture was warmed to 50 ꢁC for 30 min
to allow the reaction to reach completion.20
2.3.2.
Bis(4-methoxyphenyl
thiocarbonyl)disulfide
1f.16 Red crystals, mp 156–158 ꢁC (acetonitrile),
13.4 g (73%); 1H NMR (300 MHz, CDCl3) d (ppm): 8.19
(d, J = 9.0 Hz, 4H, H-2/6), 6.93 (d, J = 9.0 Hz, 4H,
H-3/5), 3.88 (s, 6H, CH3O–); 13C NMR (75 MHz,
CDCl3) d (ppm): 218.14 (C@S), 164.58 (C-4), 137.24
(C-1), 130.25 (C-2), 114.03 (C-3), 55.57 (CH3O–).
The solution was cooled to 0 ꢁC and p-tosyl chloride
(9.6 g, 50 mmol) in 40 ml of THF was added dropwise
over 45 min after which the reaction mixture was stirred
for another hour. The colour changed to brown and a
solid precipitated. The solution was concentrated to
30–40 ml and the solids were filtered off. Recrystalliza-
tion was carried out twice, firstly from acetonitrile and
secondly from chloroform.
2.3.3. Bis(4-fluorophenyl thiocarbonyl)disulfide 1g.15
Purification was done by column chromatography on
silica gel with chloroform as solvent.
Red crystals, mp 129–131 ꢁC (decomposition, aceto-
nitrile), 9.7 g (61%); 1H NMR (300 MHz, CDCl3) d
(ppm): 8.04 (dd, J = 4.0, 1.1 Hz, 2H, H-5), 7.77 (dd,
J = 5.1, 1.1 Hz, 2H, H-3), 7.21 (t, J = 5.1, 4.0 Hz, 2H,
H-4); 13C NMR (75 MHz, CDCl3) d (ppm): 205.63
(C@S), 149.98 (C-2), 137.07 (C-4), 129.21/128.71 (C-3/5).
1
Red solid, 10.1 g (59%); H NMR (300 MHz, CDCl3) d
(ppm): 8.16–8.12 (m, 4H, H-2/6), 7.16–7.12 (m, 4H,
H-3/5); 13C NMR (75 MHz, CDCl3) d (ppm): 217.32
(C@S), 165.20 (C-4), 139.84 (C-1), 130.06 (C-2), 115.78
(C-3).
The structure of 1h was further confirmed by X-ray
analysis. Crystallographic data (excluding structure fac-
tors) for the structure have been deposited with the
Cambridge Crystallographic Data Centre as supplemen-
tary publication number CCDC 601487. Copies of the
data can be obtained, free of charge, on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK [fax: +44 (0)1223 336033 or e-mail: deposit@
ccdc.cam.ac.uk].
2.3.4. Bis(dimethyl thiocarbamyl)disulfide 1i. White
crystals, mp 155–156 ꢁC (ethanol), 18.4 g (77%); MS:
240 (M+). A sample of commercially available 1i
(tetramethylthiuram disulfide, [137-26-8], Aldrich) was
used as reference.
2.3.5. Bis(4-methylphenyl) disulfone 2.17–19 White crys-
tals, mp 221–222 ꢁC (acetone); 1H NMR (300 MHz,
CDCl3) d (ppm): 7.87–7.81 (m, 4H, Ar), 7.45–7.40 (m,
4H, Ar), 2.48 (s, 6H, CH3); 13C NMR (75 MHz, CDCl3)
d (ppm): 148.31, 131.67, 130.53, 128.27, 21.82.
The preparation of disulfide 1h by oxidation of the free
2-thiophenecarbodithioic acid with DMSO or its potas-
sium salt with I2/KI solution resulted in crude yields of
only 5% and 12%, respectively.
For comparison purposes 2 was independently synthe-
sized by reaction of p-tosyl chloride with sodium
4-methylphenyl sulfinate.
3. Conclusions
2.4. Method B2
The synthesis of bis(thiocarbonyl)disulfides following the
presented protocol is efficient and results in satisfactory
yields of the desired products. Purification of the products
2.4.1. Bis(2-thienyl thiocarbonyl)disulfide 1h. A Grig-
nard solution, prepared from 2-bromothiophene
(16.3 g, 100 mmol) and magnesium turnings (4.85 g,